Battle of the Granicus was the major battle of Alexander the Great campaign in Asia. After crossing the Hellespont (now Dardanelles) he was met by the army of Persian Empire. The general of emperor Darius III fought they will teach the Greeks a lesson, so they didn’t even bother to gather enough forces - they put about 25,000 people against 36,000 experienced Macedonians.
The battle was decisive victory for Alexander - while losing about 300-400 men he killed about 4,000 and captured 2,000, including many Greek mercenaries fighting for Persia.
Story of Alexander the Great and his campaing to Asia - from the first battle to the ruling of almost whole world known to anscient geography.